As a rule, a rotor intended for a rotary-wing aircraft comprises a rotor shaft or rotor mast, a rotor head and one or more adjustable rotor blades that are non-rotatably joined via the rotor head to the rotor shaft or rotor mast. For purposes of cyclic and collective blade angle adjustment, such a rotor has an actuation system whose essential elements are a mixer lever gear with actuators and a control linkage, a swash plate that has a non-rotating part and a rotating part, that is arranged around the rotor shaft or rotor mast and that interacts with the mixer lever gear, said rotor also has a swash plate carrier as well as blade control rods that interact with the swash plate and with the rotor blades or with their blade adjustment levers. In order to effectuate the cyclic and collective control or blade angle adjustment, the swash plate can be moved in the axial direction of the rotor shaft by means of the mixer lever gear and it can be tilted in several planes.
With more modern rotor concepts—which are known as fly-by-wire or fly-by-light controls—the cell-sided parts of the control linkage, which extend all the way to the swash plate, or even the entire mixer lever gear are replaced by electric conductors or fiber-optical waveguides. Control signals generated by the pilot are transmitted via these conductors. These control signals then, in turn, control actuators that move the swash plate. Special control variants such as, for example, the so-called higher harmonic control (HHC), which is especially advantageous for suppressing noise and vibration on the rotor, do not perform satisfactorily with this technology.
Moreover, rotors with individual blade control (IBC) are known. With such a rotor, the control rods from the swash plate to the blade adjustment levers of the rotor blades are replaced with lengthwise adjustable actuators. These actuators are regulated individually and thus control the rotor blades individually.
The report titled “Eighteenth European Rotorcraft Forum,” Paper No. 16, “Development of active control technology in the rotating system, flight testing and theoretical investigations” describes a rotor having IBC with which the individually controllable, lengthwise adjustable actuators are supported on a rotating part of a swash plate that can be moved and tilted axially, said actuators extending away from this part approximately parallel to the lengthwise direction of the rotor shaft upwards to the blade adjustment levers. When the rotor rotates, the actuators revolve around the rotor shaft together with the rotating part of the swash plate and with the rotor blades. Thus, there is a relative movement between the actuators and the stationary part of the swash plate as well as between the rotating part of the swash plate and the rotor shaft.
German utility model G 89 09 165.5 likewise discloses a rotor with IBC, which is similar to the IBC concept described in the preceding paragraph. The individually controllable, lengthwise adjustable actuators each engage at one end with a blade adjustment lever and at the other end with a swash plate-like element. German utility model G 89 09 165.5 does not indicate exactly how this swash plate-like element is configured.
All of the above-mentioned rotor concepts use a swash plate or a swash plate-like element as a mechanical component.
British patent GB 2 149 372 A discloses a coaxial rotor consisting of two individual rotors for a helicopter, having a rotor blade control with which the rotor blade adjustment of each rotor is effectuated by means of an electromotor actuator system that has an electric rotor and a stator. The stator is arranged on a hollow axle which is immovably joined to the cell structure of the helicopter and through which a drivable rotor shaft runs. The electric rotor, in turn, is arranged on an element that rotates along with the rotor blades and is joined to the rotor blades by a kind of intermediate gear. The rotor blade is adjusted by a relative movement between the electric rotor and the stator. In this concept, there is also a relative movement between those parts of the coaxial rotor that comprise the stator and those parts that comprise the electric rotor and the intermediate gear. This construction is highly complex and intricate, it is relatively heavy and it consists of many moving parts.
Moreover, rotors are known with which the rotor blade control is effectuated without a swash plate. Instead of the swash plate, a so-called control spider is used here. Among other things, this concept has a control rod extending through a hollow rotor shaft as well as a special bearing and swiveling means to make the transition from a non-rotating to a rotating part of the rotor and of the control spider system. Such rotors were used, for example, in the Westland WG13 (Lynx) helicopter or in the Bristol Sycamore helicopter. In actual practice, however, they have been replaced by more modern rotors with swash plates.
The control systems of the prior-art rotors are very safety-critical, mechanically and kinematically highly complex, they are extremely heavy due to the need to be fail-safe over a long service life, they have a large overall volume and, as a result, a high aerodynamic resistance.
Moreover, they are quite susceptible to external effects or damage, whereby—due to their design and exposed location on the rotor—they are actually at greater risk of being damaged.